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    <script>
        function fn(a,b){
            console.log(a,b);
        }
        // 函数调用时，实参比形参个数少
        fn(1); // 没有接收到值的形参，值都是 undefined
        // 函数调用时，实参比形参多, 有的形参正常接收数据，超过的实参，也不会报错
        fn(1,2,3);
    </script>
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